High-Speed CBJT Operational Amplifier with AB Class Input Stage

A circuit technique for increasing the maximum slew rate (SR) of the output voltage of a classical CBJT operational amplifier (OpAmp) with an AB class input stage, which has become the basis for several commercially available microcircuits, is discussed. For this purpose, two additional differentiating capacitors are provided in the input stage to increase the SR by 1-2 orders of magnitude. The results of computer simulation of the CBJT OpAmp for a typical silicon technological process with micron topological standard are presented, which showed that the SRₘₐₓ limits for the falling edge of the transient increase from 123V/μs to 12000V/μs. The OpAmp considered in this article is intended for use in a subclass of so-called discrete-to-analog SC filters on switched capacitors, which (in some important cases) require higher SR values. In addition, the use of such OpAmp is relevant in drivers of high-speed analog-to-digital converters and other devices of automatics and computer engineering.